Vulcanization of rubber



Patented Oct. 3, 1933 a t v V UNITED STATES; T NT OFFICE.

VULCAVNIZALTION F RUBBER Ira Williams, Woodstown, N. J., and-Carlton W.

' Croco, Wilmington,-Del., assignors to E1. (in l Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing.j Application March 4, i932 Seflal'No. 596,898 33 Claims. (Cl.,1 8-53) This invention relates to the vulcanization of ammonium, zinc, cadmium and lead salts or salts rubber andmore particularly to anew class of of other metals which readily form chlorides. vulcanization accelerators therefor. .I Since the'majority of these salts are solids, it is Mercapto benzothiazole andmany of its deriva-, most satisfactory to. either dissolve the salt in a tives such as the normal and basic lead or zinc liquid medium or to suspend it in finely pulverized 6 salts; themonoand polysulfides; the guanidine' state in aliquid medium. g salts; the reaction products of mercapto benzo- 'The liquid medium should be one with which" thiazole and aldehyde-amine condensation prodthe carbonyl chloride reacts less readily than ucts; the dinitro chlor phenyl derivatives; and with the salt. Forexample,'wherethefsodium 10 the reaction products of mercapto benzothiazole, or potassium salts are employed, either water or amines and chlorine derivatives of carbon disulalcohol may be usedas thesolvent or suspendfide have been proposed as accelerators for the ing medium. Where'the-zinc salt is employed, vulcanization of rubber. Mercapto benzothiazole alcohol is less satisfactory because the slower and many of these derivatives are excellent acaction between the zinc salt and carbonyl chlo- 15 celerators but have the disadvantage that the ride permits much of the carbonyl chloride to re- 1 accelerating action is exerted at ,relatively low act with the alcohol, Accordingly, where the temperatures often causing burning a or pre- Zinc and similar saltsare employed, acetone, benvulcanization on the mixing mills, thereby prozone, carbon tetra chloride or gasoline will be ducing a rubber of inferior physical properties. found to be the more satisfactory liquid suspend- 20 An object of thepresent invention is to provide ing media. For the more ready separation of a new class of chemical compounds. 7 A second the productsof thereaction and the recovery of object is to provide a new class of easily prepared the pure compound, it is desirable to employ, as vulcanization accelerators. A third object is to the liquid-medium, a substance in which one of provide a class of vulcanization accelerators havthcproducts of the reaction is insoluble and the 25 ing the accelerating characteristics of mercapto other product: is soluble If'the liquid medium 1 benzothiazole at elevated temperatures, but which is water or if moisture is present, it is also deare less active at low temperaturesand thus will sirable to maintain the liquid slightly alkaline not cause scorching or pre-yulcanization in the in der to Ob the pu est P t. mixing mill. Further objects are to provide a We have also found that it is desirable to main- 30 new composition of matter and to advance the art. tain the materials in the reaction vessel well Other objects will appear hereinafter. agitated during the addition of the carbonyl chlo- These objects are accomplished according to ide a d t ug the entire period Of the the present invention which comprises reacting action. While the temperature during the resalt of a, mercapto benzothiazole with carbonyl action may be varied within rather wide limits,:

35 chloride under such conditions that the chloride it is desirablezto. maintain. the temperature at of the salt forming element or group is split off about or below 40 C. for the most economical and a dibenzothiazyl l-ss dithio carbonate. is Operation r formed, a Q The salts-of any of the mercapto benzothia- Our invention is based upon the discovery that 8 mp und may be p yed in this'proccarbonyl chloride will react with salts of mer- O Q the mpounds Ofthis class which capto bemothiazoles to form new chemical comwe have found to produce particularly valuable pounds not heretofore known in the art and vulcanization accelerators'are those formed from which are particularly adapted for accelerating the salts of mercapt benzothiazole, h the vulcanization or rubber. m r p b mo hi l ,v 5 h0Xy1-mercapto In general, the'process of preparing these new b z thiazo fi ap O ia- I compounds comprises first preparing a suitable zole, 4-.methy1-1-mercapto benzothiazole, '5- salt of mercapto benzothiazole, then dissolving methyl-l-mc c p e t y or suspending this salt inasuitable liquid'medium, l-mercapto benzothiazole, and 3:5-dimethy1-1- and then passing carbonyl chloride into the solumercapto t a e.

501 tion or mixture, with agitation, until the mer- 'In order. to more clearly illustrate the precapto benzothiazole salt has reacted with the ferred methods of preparing these compounds, carbonyl chloride. While'any salt of a mercapto the following examples are given: a a benzothiazole which will react with carbonyl chlo- Erample L Sixty-four and eight-tenths (64.8) a ride maybe employed, we have discovered that pa ts by Weight f m t benzothiazole were the most suitable are the sodium, potassium, add'edwith 16 parts of sodium hydroxide to 4000 0 carbonylchloride waspassedinto themixture' parts of water stirred until all was dissolved. This solution was then cooled to about 10 C. and, while being rapidly stirred, a stream of carbonyl chloride was'led in. A dilute sodium hydroxide. solution was run in .at sucha rate that the solution remained'alkaline'. Theaddition of.

the carbonyl chloride was continued until no more precipitate was formed in afiltered test portion when treated with carbonyl chloride. After the reaction was complete the accelerator was filtered oil and dried. Theresulting product is a pale yellow solid, solublein benzene, andmelts with decomposition at about 134 C. V 7

Example 2.-Twenty and five-tenths (20.5) parts by weight of the potassium salt of mercapto benzothiazole were finely ground and suspended. in 100 parts of dry'benzene. Five parts of'car bonyl chloride were dissolved in 50 parts of dry benzene. Both solutions were cooled andmixed at about 5 C. The stirring was continued for 30 minutes, after whichtime, the precipitated potassium'chloride wasfiltered off. The accelerator was recovered by evaporation of the benzene. I i

Ema'mple 3. The processoi Example 2'-was followed except that dry acetone was employed in place of the benzene.

EacampleL-Forty (40) parts of the zinc salt of mercapto benzothiazole were suspended in 300 parts of benzene. '"After cooling to about 10 C.

until theweight 'hadl inc'rased 10 parts. Stirring was'continued tor BOminutes. The product was filtered and the accelerator recovered by evaporation of thefiltrate.

Dibenzothiazyl 1-ss'- dithio'carbonate is a moderately active accelerator at high vulcanization 7 temperature, but is. weak when lower temperatures are employed. This is a distinct advantage since itpermits millingjcalendering, and similar operations, whichdevelop considerable'heat, to

be carried out with'greater freedom from scorching difficulty. This difierencemay be'illustrated by vulcanizing a compound consisting of 100 parts of rubber, 25parts of carbon b1ack,.5 parts of zinc oxide, 3 parts of sulfur, and 1 partof dibenzothiazyl l -ss' dithio carbonate. When this mix 'was vulcanized for 15 minutes at .287 F. and tested, the load at 500% elongation a'mounted to 1025 pounds per square inch. However, when the vulcanization was 'carried' on at 259 Fffor 15minutes, the same test'showed a load of only 175 pounds per square inch at 500% elongation.

In the above examples, we have disclosed processesemploying salts of mercapto benzothiazole. However it is understood that the same processes may be employed with salts of substituted mercapto'benzothiazoles, some of which have been mentioned. Other substituted mercapto benzothiazole compounds, the saltsof which deserve special attention are the mercapto benzothiazoles having one or more ethyl groups substituted in the benzene ring, the'methoxy'benzothiazoles, and in fact, the'alkyl and alkoxy substituted mercapto benzothiazoles generally. The

be understoodthat such-"term includesnot only' mercapto benzothiazole but also the various substituted mercapto benzothiazoles.

"While we have disclosed certain specificcompounds and compositions of matter and certain specific methods of preparing the same, it will be'apparenttothose skilled infthe art that many other compounds and compositions of matter may be, prepared and the processes of preparing the same may be variously modified and variations may be made in the proportions employed withoutydeparting fromthe spirit of our invention. Accordingly,"theyscope of our invention is tobe limitedsolelyby the appended claims construed as broadly as is permissible in View of the prior art. I

We claim: V 1 ."iA, newcomposition of matter which comprises'a dibenzothiazyl l-ss dithio carbonate.

2. The method of preparing a new chemical compound which comprises reacting a salt of a mercapto benzothiazole with carbonyl chloride.

3.:The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of mercapto benzothiazole, thei reacting compounds being in such proper combine with two molecules of the mercap to benzothiazole. z

4. The methodof preparing anew chemical compound which comprises reacting carbonyl chloride with an inorganic salt of a mercapto benzothiazole, the reacting compounds being in such proportion that they will combine in the rates of two molecules of the mercapto benzothia'zole to one molecule of carbonyl chloride.

5. The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of a mercapto benzothiazole in a liquid medium less reactive to carbonyl chloride than the salt, the reacting compounds being in such proportion that they will combine in the'ratio of two molecules of the mercapto benzothiazole to one molecule of carbonyl chloride. Q a

6, The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of a mercapto benzothiazole in a liquid medium less reactive to carbonyl chloride than the salt and in'which one of the prodnets of the reaction is insoluble and the other product is soluble, the reacting compounds being in such proportion that they will combine in the ratio of two molecules of the mercapto 'benzothi azole'to one molecule of carbonyl chloride;

- '7.= The method of preparing a new chemical compound which comprises reacting carbonyl chloridewith a salt of a mercapto benzothiazole in a liquid medium less reactive to carbonyl chlo-. ride than the salt and maintaining the temperature of the reaction at about 40 C. or less, the reacting compounds being in such proportion that they will combine-in the ratio of two molecules of the mercapto benzothiazole to one mole cule of carbonyl chloride. I

8. Rubber having incorporatedtherein, as a vulcanization acceleraton'a dibenzothiazyl l-ss dithio carbonate.

-9. ;The method of making vulcanized rubber which comprises I mixing unvulcanized rubber with'vulcanizing substances and a dibenzothiazyl l-ss dithio carbonate and then vulcanizing the mix.

- 10. A new composition of matter-which comprises dibenzothiazyl l-ss'fdithio carbonate.

11. A new composition of matter which, comtions that o'nemolecule of carbonyl chloride will prisesa member of the group consisting of alkyl and alkoxy substituted dibenzothiazyl l-ss dithio carbonates.

12. A new compositionof matter which comprises a dibenzothiazyl l-ss dithio carbonate derived from a methyl-l-mercapto benzothiazole.

13. A new composition 01' .matter which comprises a dibenzothiazyl l-ss' dithio carbonate derived irom 3 -methyl-1-mercaptobenzothiazole.

.14. A new composition of matter which comprises a dibenzothiazyl l-ss dithio carbonate derived from an ethox'y-l-mercapto benzothiazole.

15. A new composition of matter which comprises a dibenzothiazyl l-ss' dithio carbonate derived from 5-ethoxy-1-mercapto "benzothiazole.

16. The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of .mercapto benzothiazole, the reacting compounds being in such proportions that one molecule of carbonyl chloride will-combine with two molecules of the .mercapto benzothiazole.

. 17. The method ofpreparing a new chemical consisting oi alkyl and alkoxy substituted mercapto benzothiazoles, the reacting compounds being in such proportions that one molecule of carbonyl chloride will combine withtwo molecules of the mercapto benzothiazole.

18. The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of a methyl-l-mercapto benzothiazole, the reacting compounds being in suchproportions'that one molecule of carbonyl chloride will combine with two molecules of the mercapto benzothiazole. V. v

19. The method of preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of 3-methyl-l-mercapto benzothiazole, the reacting compounds being in such proportions that one molecule of carbonyl chloride will combine with two moleculesof the mercapto benzothiazole.

20. The method of preparing a new chemical compound which comprises reactingI carbonyl chloride with a salt of an ethoxy-l-mercapto benzothiazole, the reacting compounds being in such proportions that one molecule of carbonyl chloride will combine with two molecules of the mercapto benzothiazole.

21. The method 01. preparing a new chemical compound which comprises reacting carbonyl chloride with a salt of 5 -ethoxy-l-mercapto benzothiazole, the reacting compounds being in such proportions that one molecule of carbonyl chloride will combine with two molecules of the mercapto benzothiazole.

22. Rubber having incorporated therein, as a vulcanization accelerator, dibenzothiazyl l-ss "dithio carbonate.

23. Rubber having incorporated therein, as a vulcanization accelerator, a member of the group consisting of alkyl and alkoxy substituted dibenzothiazyl 1-ss dithio carbonates.

' 24. Rubber having incorporated therein, as a vulcanization accelerator, a dibenzothiazyl l-ss dithio carbonate'derived from an ethoxy-l-mercapto benzothiazole. 1

2'7. Rubber having incorporated therein, as a vulcanization accelerator, a dibenzothiazyl l-ss dithio carbonate derived from 5-ethoxy-1-mercapto benzothiazole.

' 28. The method of making vulcanized rubber which comprises mixing unvulcanized rubber with vulcanizing substances and dibenzothiazyl l-ss' dithio carbonate and then vulcanizing the mix.

29. The method of making vulcanized rubber which comprises mixing unvulcanized rubber with vulcanizing substances and a dibenzothiazyl l-ss' dithio carbonate derived from a member of the group consisting of alkyl and alkoxy substituted l-mercapto benzothiazoles and then vulcanizing the mix.

30. The method of making vulcanized rubber which comprises mixing unvulcanized rubber with vulcanizing substances andadibenzothiazyl l-ss' dithio carbonate derived from a'methyl-lmercapto benzothiazole and then vulcanizingthe mix. f I

31. The methodof making vulcanized rubber which comprises mixing unvulcanized rubber with vulcanizing substances and the dibenzothiazyl 1-ss dithio carbonate derived from 3- methyl-l-mercapto benzothiazole and then vulcanizing themix. I

32. The method of making vulcanized rubber which comprises mixing unvulcanized rubber with vulcanizing substances and a dibenzothiazyl 1-ss" dithio carbonate derived from an ethoxy-l-mercapto benzothiazoleand then'vulcanizing the mix. 33. The method of making vulcanized rubber which comprises mixing unvulcanized rubber CERTIFICATE or CORRECTION.

Patent No. 1, 928,773. October 3, 1933.

IRA WILLIAMS, ET AL.

it is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 1, after "water" insert the word and; line 99, claim 3, after "of" insert the article a; and line 109, claim 4, for "rates" read ratio; page 3, line 88, claim 25, for "3- methyi-mer-" read 3-methyl-l-mer-; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 28th day of November, A. D. 1933.

F. M. Hopkins (Seal) Acting Commissioner of Patents. 

